Nuchal translucency scans complicated by nuchal cord – Are we measuring correctly?

Abstract

Objective To evaluate the affect nuchal cord (NC) may have on nuchal translucency (NT) thickness. To identify the sonographic features of NC complication in NT scans and to determine how these features are interpreted by sonographers complying to current Fetal Medicine Foundation (FMF) NT imaging guidelines. Methods Retrospective review of 200 consecutive NT scans was performed by three FMF accredited sonographers in a 6 month period. Where a single measurement, at the thickest portion of the NT was used for combined first trimester screening (CFTS) calculation a ‘standard’ NT measurement was said to have occurred. A nuchal cord, nuchal translucency (NCNT) measurement was said to have occurred if any single image displayed two NT measurements, with calipers placed measuring NT thickness above and below the NC. Results The combined data from the three sonographers showed no significant deviation from the current FMF NT for crown rump length (CRL) database range. Conclusion NC was found to add only 0.3 mm to NT thickness when the median NT without NC was compared to the mean of the highest NT value (either above or below cord. Separation of the NT into separate compartments, or a slight indentation in the outer NT skin line is not always due to the presence of NC and may be the result of beam shape artefact.